Supplementary Material for: Association between Allergic Diseases and Irritable Bowel Syndrome: A Retrospective Study

Background: The relationship between allergic disease and irritable bowel syndrome (IBS) is poorly understood. We aimed to investigate the potential association as well as the underlying immunological mechanisms. Methods: A retrospective case-control study of 108 atopic patients from among outpatients in an allergy clinic (allergic rhinitis [AR], n = 49; chronic urticaria [CU], n = 59) and 74 controls from among ward companions was conducted from November 2016 to March 2017. The detection rates and related gastrointestinal (GI) symptoms of IBS, as well as immunological indices, were calculated. Results: CU patients had a trend of increase in the detection of IBS compared to controls (OR = 4.846; 95% CI 0.967–24.279, p = 0.077). Loose stools (OR = 2.406; 95% CI 1.075–5.386, p < 0.05) and viscous stools (OR = 2.665; 95% CI 1.250–5.682, p < 0.05) were more common in CU patients. Atopic patients positive for serum total immunoglobulin E (IgE) (OR = 3.379; 95% CI 1.088–10.498, p < 0.05) or house dust mite (HDM)-specific IgE (OR = 3.640; 95% CI 1.228–10.790, p < 0.05) were more likely to have abdominal bloating. Besides, a positive association between levels of total IgE and severity of abdominal bloating was observed (p < 0.05). An HDM-specific IgE-positive reaction was independently associated with abdominal bloating in atopic patients (p < 0.05). Conclusions: Allergic disease has a clear clinical association with IBS with more frequent and severe symptoms of IBS. CU patients have a tendency to suffer from IBS, usually with diarrhea. Serum total IgE and HDM-specific IgE are positively correlated with GI symptoms in atopic patients.